Stayed there for 2 nights a couple of years ago. It was my first visit to Udon. I loved my introduction to Udon but I will not be staying at the Napali again.
On the plus side they have a nice swimming pool and the grounds are attractive. The rooms are acceptable for Thailand standards and Mambo disco on Friday nights is not to be missed. This disco has a very good show on stage and go-go dancers on the central bar counter. Very loud music for those who don't like noise. But I can't praise Mambo disco enough.
As for the minus side, well I turned up there without a booking. There were about 2 or 3 cars in a very generous size carpark and when I asked is there a vacancy I was told no we are full. Then she checked the computer and said she has 1 room for 1 night only. You could fire a gun in the place and not hit anyone!!!
Stayed the night and when checking out in the morning I asked out of curiosity is there any rooms and the young lady (day shift now) said yes we have many many rooms.
So I stayed one more night and thoroughly enjoyed Udon but totally frustrated with the language barriers encountered at the Napali.